For several years, protein hydrolysates have given rise to an interest in cosmetic and therapeutic applications.
Protein hydrolysates can have different origins: animal, in particular fish, vegetable, or fungal, for example yeast.
The presence or absence of biological activity of a protein hydrolysate depends, in particular, on the nature of the start proteins.
Thus, the hydrolysis of fish proteins allowed obtaining hydrolysed proteins with a particular spatial structure recognised by certain receptors. Activities of hormonal and opioid type have thus been emphasised (Legal and Stenherg. Biofutur, No. 179, 1998, pages 61 to 63).
Certain documents of the prior art mention the use of yeast protein hydrolysates in cosmetic compositions. These yeast protein hydrolysates are obtained either through the hydrolysis of yeast whole cells or through the hydrolysis of the yeast soluble fraction (the cytoplasmic content).
Thus, application patent EP 0 695 801, describes the cosmetic use of a peptide composition obtained through:                a stage of yeast thermal treatment followed by a treatment with lytic enzymes of the yeast cell wall, in order to obtain a blending,        a protein purification and separation stage of the aforesaid blending, in order to obtain yeast proteins, and        an hydrolyse state of the aforesaid proteins.        
The lytic enzymes of the cell wall used in this document are enzymes attacking glucans and destabilising the wall and membrane. Thus, such a composition has hydrolysed proteins obtained from the yeast soluble fraction.
Patent application EP 0 126 364, describes the cosmetic use of a product with no histamine, non-pyrogenic, sterile, active obtained through a process comprising the following stages:                yeast plasmolysis and homogenisation to a temperature lower than 0° C.,        treatment with a proteolytic enzyme for at least 70 hours,        treatment with a diamine oxidase in order to eliminate substances having histamine,        fractional precipitation with a blending of alcohols in order to eliminate residual proteins.        
Thus, the final product has yeast-hydrolysed proteins obtained from the hydrolysis of whole yeast proteins. The implementation of such a production process shows many drawbacks, in particular, the duration of the process, the multiplicity of stages and the need of working under sterile conditions.
Application patent of EP 0 237 398, describes the cosmetic use of polypeptides biologically active obtained through the process comprising the following stages:                mechanical crushing of natural substances, for example yeasts, in order to obtain an aqueous homogenate,        enzymatic hydrolysis with a hydrolysis agent consisting of α-chymotrypsin and possibly trypsin, in order to obtain an hydrolysate,        separation of a polypeptide fraction with a specific molecular weight.        
Thus, the polypeptide fraction derives from the protein hydrolysis obtained from whole yeasts. In particular, the polypeptide fraction has a molecular weight lower than 10,000 Da and higher than 1,000 Da.
Consumers increasingly require <<natural>> products, whether in the food, cosmetic or pharmaceutical field.
In the cosmetic and pharmaceutical field, there is a real need to give new active natural substances that:                have improved cosmetic or therapeutic qualities, such as moisturising, anti-aging effects and/or firmness; and/or        an excellent stability in time; and/or        the production of which is homogeneous and/or the production process is easily implemented on industrial scale.        